10-06-2009, 04:12 PM | #1 |
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Valve lift VS. Port velocity question.
Ok guys, most of you know I'm running GT40 Irons on my car, with the E303 cam (set @ 4* ADV), and the Crane/Cobra 1.7 RR's. When I went with the 1.7's, I understandably lost a tiny bit of bottom end torque due to changing the powerband of the cam. I know as valve lift increases, port velocity decreases. According to this, the GT40's make power all the way up to .600" of lift.http://www.allfordmustangs.com/Detailed/630.shtml However, they don't make THAT much more at .600" than they do at .500". Do you think the 1.7's are hurting me more than they're helping? I know bigger isn't always better in some cases. When I dynoed it a couple of months ago, it made power up to 5200 RPM's, which I know is mostly the intake.
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Eric 89 LX Coupe-Juiced 01 Lightning-Boost 06 TBSS |
10-06-2009, 04:16 PM | #2 |
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You also have to consider that changing the rocker ratio effectively changes the opening & closing event timing, not just the maximum lift at the valve.
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10-06-2009, 04:56 PM | #3 |
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It also increases the duration IOW.
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Eric 89 LX Coupe-Juiced 01 Lightning-Boost 06 TBSS |
10-06-2009, 05:44 PM | #4 |
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Yep, I guess that's what I was getting at. The opening and closing happen faster. You've basically got a "bigger" cam than with the 1.6s and shifted your torque curve later in rpm range, possibly losing some down low.
How does it feel in the higher rpms? |
10-06-2009, 05:51 PM | #5 |
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Feels plenty strong and torquey from around 2400 and up.
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Eric 89 LX Coupe-Juiced 01 Lightning-Boost 06 TBSS |
10-06-2009, 07:12 PM | #6 |
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10-06-2009, 09:03 PM | #7 |
3v's are slow
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Doesn't the 4 degrees cam advance you have bring the powerband back down or am I thinking backwards
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10-06-2009, 09:49 PM | #8 |
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No, you're right. I was planning on putting it back at 0* awhile back, but since the Explorer intake drops off after 5200 anyway, I decided to leave it alone.
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Eric 89 LX Coupe-Juiced 01 Lightning-Boost 06 TBSS |
10-06-2009, 10:08 PM | #9 |
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Are we gonna see what kind of "shot" you have at trackday this year?
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10-06-2009, 10:16 PM | #10 |
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Not much more you can get out of a 220º duration cam (E303). If you wanna really benefit, put some more camshaft in it. I wouldn't hesitate to go somewhere around 228º duration, but I wouldn't mess with anymore than about .500 lift on the heads.
As for your question, the 1.7's are not hindering the E303 on your combo.
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